The present invention relates to a thick matter pump comprising at least two pump units alternating in the pump and suction mode, a delivery line, a suction line, and a switching valve for switching between the pump units, one pump unit being connected in the pump mode by the switching valve to the delivery line, and one pump unit being connected in the suction mode to the suction line.
Thick matter pumps are used in very many cases for conveying concrete, but materials of a similar type can also be conveyed by such pump units. Known are, in particular, pump arrangements in which the pump units are formed by cylinder/piston pumps which are alternately connected via a pipe slide to a delivery line or to a suction line. There are arrangements in which the pipe slide is arranged within a supply container and in the suction mode the cylinder/piston pump directly sucks the thick matter from the supply container. The supply container is upwardly open in most cases, so that thick matter can be refilled.
In other pump constructions, a suction line terminates at the lower end of a supply container, the thick matter being discharged through the suction line. A conveying unit, e.g. a screw, can also be arranged thereby in the supply container for ensuring a better filling degree. The other end of the suction line section leading away from the supply container is followed by a pipe slide housing, which ensures a suitable switching between the pump units and a connection of the pump unit either to the delivery line or to the suction line.
With all of these different pump constructions, attempts are made to produce a pump flow which is as continuous as possible, despite the switching operation of the pipe slide.
In a generic construction which is disclosed in DE 197 35 091 A1, a well-known activation method for the pump units is resorted to and used with a pipe slide device arranged outside of the supply container. In this known method the cylinder/piston pump operates faster in the suction mode than in the pump mode, whereby the suction operation of the one pump unit is already completed while the pump operation of the other pump unit still continues. Subsequently, the thick matter fillings which are in contact with the first pump unit are separated from the supply container by means of slide elements, which are also known. The thick matter is subsequently precompressed by means of the delivery piston of the first pump unit until a desired pressure is built up. Meanwhile the second pump unit is still in the pump mode. It is only after the application of the preloading pressure that the pipe slide switches over. The one end of the pipe slide is in permanent contact with the suction line section leading away from the supply container, whereas the delivery line is in permanent communication with the cavity of the pipe slide housing. The preloaded thick matter comes now in contact with the pressurized thick matter in the pipe slide housing. This operation does not lead to any vibrations in the delivery column because the preload is preferably at the pressure level in the delivery line and the thick matter column does therefore not slump in the delivery line. As soon as the second pump unit has completed its pumping operation, the first pump unit takes over the pumping operation. Subsequently, the second pump unit is connected to the supply container by means of the pipe slide and by opening the slide. The cycle starts again with exchanged pump units.
Constructions in which the pipe slide is in permanent communication with the delivery line and the suction line section leads to the pipe slide housing can also be operated with such a method on condition that corresponding slides are used. See, for instance, the construction in DE 196 41 771 A1.
Said constructions, however, have the drawback that part of the delivery volume of the pump units is wasted because of this preloading operation. That is why the pump units must have a larger size than would be necessary.
It is therefore the object of the present invention to provide a thick matter pump of the above-mentioned type which allows an improved design of the pump units.
To this end a pressure boosting device which is independently operative of the pump units is provided according to the invention in the area of the suction line for actively effecting a thick matter precompression.
This means that, either independently of the pump unit or in support thereof, there is provided a separate device which from the direction of the suction line effects a pressing of the thick matter for providing a precompression. When a cylinder/piston pump is used, the necessary path for a precompression is reduced thereby, or a path is no longer needed at all when the pressure boosting device entirely takes over the precompressing operation. Thus, the pump units need no longer convey the very volume required for precompression. This reduces the size of the pump units. Moreover, this yields a further positive effect. Thanks to the active pressing of the thick matter by the pressure boosting device, the pump unit and suction line, respectively, are filled in an improved way. So far the cross-sections of the openings of cylinder/piston pumps have required a specific size, for instance for concrete, so that a high filling of the cylinder could be achieved by the action of negative pressure. The size of this opening can now be reduced due to the continuous supply of the thick matter by the pressure boosting device. This, however, has also the effect that the pump units can be arranged closer to each other and the switching times can thereby be reduced considerably, e.g. by using a pipe slide. The elements which follow the openings, for instance pipe slides, etc., can also be reduced in size, which is of great advantage in particular with respect to the forces acting within the system due to the thick matter pressure. Thick matter which is difficult to suck can also be pumped with the help of a pressure boosting device without any problems. Moreover, the pump unit can be operated in the suction mode at a faster pace because the losses in the sucking action can be compensated by the pressure boosting device. A separate pressure boosting device is excellently suited for a later modification of existing thick matter pumps. When existing pump units are kept and when the separately acting pressure boosting device is now used in addition in accordance with the invention, the pumping efficiency can be improved by up to 20% due to the better filling of the pump unit in the suction mode.
In an advantageous embodiment, the suction line comprises an elastically deformable section and the pressure boosting device comprises squeezing elements by which the elastically deformable section of the suction line can be compressed for increasing the pressure. Advantageously, such a deformable section can be connected to a supply container. Suitable squeezing elements will then ensure a closing of the elastically deformable section with subsequent pressure build-up. Due to the relatively low compressibility of the thick matter, air inclusions must mainly be overcome. The deformable section is therefore deformed to such a degree that the desired pressure build-up is achieved in the suction line. This could also be carried out with the help of a plurality of squeezing elements. Moreover, a squeezing element may be designed with respect to its shape such that said function takes place in one operation.
Moreover, it is also possible that rotatably supported squeezing elements first compress the deformable section and thus close the suction line and are then moved towards the pump unit. This process reminds of the delivery of media by means of a hose pump. That is why according to one variant it is additionally of advantage when the elastically deformable section of the suction line is a hose piece. Hose pieces that withstand correspondingly high pressures are very well known in the prior art.
Hose pumps are already used in part for conveying concrete, so that enough examples can be found in the prior art with respect to the selection of the material and the reinforcement of the hose piece. Preferably, said hose piece can be interposed by means of suitable coupling elements into the suction line, which permits a rapid exchange in case of repair or wear and also permits a more flexible arrangement. Suitable hose pieces for such squeezing purposes have a sufficiently long service life.
In another variant of the pressure boosting device, said device comprises a membrane. On the one hand, a membrane can be pressurized at one side by very different media, resulting in a bulge which achieves the desired precompressing and pressing effect.
In a particularly sturdy and low-maintenance design, the pressure boosting device comprises a cylinder/piston unit. Said unit could e.g. be configured to be identical with or similar to a pump unit, preferably with smaller dimensions, and e.g. terminate laterally into the suction line.
When the pumping capacity of the pressure boosting device is greater than the suction capacity of one of the pump units, this has the additional advantage that the pressure boosting device can start its precompressing operation already during the suction operation, in particular in the end phase, and superpose the same. The suction operation and the precompression process could be matched in an optimum manner to each other such that both processes end at the same time.
Preferably, the pressure boosting device can comprise adjusting means for adjusting the thick matter compression. Advantageously, the force by which e.g. squeezing elements press onto a hose piece could be determined to this end. Thus even without a direct pressure measurement in the thick matter line, the pressure prevailing there can thereby be deduced. The pump behavior for reducing pump impacts can be optimized by adjusting the pressure. Different precompression pressures may be of relevance to the different thick materials.
To avoid damage to the thick matter pump, the pressure boosting device may comprise an overload protection for limiting the maximum precompression of thick matter. In the case of clogging or switching trouble, etc., this could be of great advantage, in particular, in order to protect an elastically deformable section of the suction line.
The pressure boosting device can operate independently or can be coupled directly with the drive of the pump units. According to one variant, it is of advantage when the squeezing elements of the pressure boosting device are operable by a hydraulic means. The hydraulic circuit for the squeezing elements can directly be coupled with a hydraulic circuit for the pump units, so that there is a direct dependence. However, all of the other possible activation constructions are also possible.
For thick matter, such as concrete, delivery cylinders with delivery pistons have turned out to be particularly suited as pump units; that is why these are preferably used according to one embodiment. The pressures desired for the delivery of concrete can be exerted by means of such pump units for achieving very high delivery heights.
Moreover, pipe slides with pivot pipe bodies have turned out to be suited for such a use as a switching valve because these turn out to be relatively insensitive to the medium to be pumped. One variant provides for a corresponding application.
The present invention could also be used with pipe slides arranged within a supply container. According to a particular development, however, the pipe slide comprises a housing which surrounds the pivot pipe body at least in portions at a distance, a cavity formed between the housing and the pivot pipe body is part of the delivery line, and the pivot body which can be switched between the pump units is part of the suction line. Such an arrangement does not create any sealing problems on the pivot pipe body (in particular S pipe) and on a plate. Moreover, there are only slight or no reaction forces acting on the pivot pipe body (in particular S pipe) and the bearing thereof.
In a further embodiment, the pipe slide comprises a housing which surrounds the pivot pipe body at least at a distance, a cavity which is formed between the housing and the pivot pipe body forms part of the suction line, and the pivot pipe body which can be switched between the pump units forms part of the delivery line. The conditions prevailing in such a variant are sufficiently known from standard constructions and can be mastered. Moreover, during the switching of the pivot pipe body the same pressure prevails as in the other embodiment because the housing is also subjected to pressure by the pressure boosting device.
Since the inner wall of the housing is in permanent contact with thick matter and a pivot pipe body slides along parts of the inner wall, at least part of the inner wall of the housing is provided at least in portions with wear elements according to one variant. Said wear elements can then be replaced.
It makes also sense when according to one embodiment the housing comprises at least one closable maintenance or cleaning opening.
Preferably, one end of the suction line is connectable to a supply container. Finally, it is possible to arrange the switching valve in a flexible manner, for instance on a concrete mixer vehicle. The filling of the suction line can also be supported by said arrangement because the full pressure of the thick matter from the supply container can act thereon.
Advantageously, the supply container is vertically adjustable and made pivotable. This is very easily possible in particular in embodiments in which the switching valve is not directly arranged in the supply container itself. The vertical adjustment also increases the filling pressure of the suction line.
Moreover, the invention also refers to a suction/pumping method for a thick matter pump employing apparatus disclosed herein. The method comprises the following steps:
connecting the delivery line to a first pump unit,
connecting the suction line to a second pump unit,
the first pump unit switching to pump mode,
the second pump unit switching to suction mode,
precompressing and pressing the thick matter into the suction line by means of a pressure boosting device performing a compressing operation independently of the first pump unit until the desired precompression or filling amount is achieved in the second pump unit.
Accordingly, the method has the advantage that a precompression can take place by means of a pressure boosting device, also independently of a pressure-applying pump unit. The pump unit is activated in a much simpler way because the precompression considerably depends on a separate operation of a pressure boosting device. Therefore, the method provides a continuous delivery flow. The method steps will then take place after a switching operation for the respectively other pump unit (first pump unit in the suction mode, second pump unit in the pump mode) until the cycle begins anew. The sequence of the individual process steps takes place partly at the same time or in overlapping fashion. In particular, the recompressing and pressing operation can take place after completion of the suction mode, in a way overlapping with the suction mode or during the suction mode with simultaneous completion.
The simplest construction is achieved when the first pump unit is at a standstill during the precompressing step by the pressure boosting device or terminates the suction mode. The optimum filling of the pump unit is then determined through the pressure boosting device. This will then correspond at the same time to the highest possible filling level by which the efficiency of the pump units can be increased to a considerable extent.
A further variant of the method is that in the end phase of the suction mode of the second pump unit the pressure boosting device is activated with a capacity superposing the suction mode of the second pump unit. The end phase will then mainly be defined by the pressure boosting device which will then press the thick matter. At the same time, however, the second pump unit completes its suction mode to assume its maximum filling position. During this whole process the desired compression of thick matter can already be obtained although the second pump unit has not yet completed its suction mode entirely.
Advantageously, the second pump unit terminates the suction mode at the same time with the precompressing and pressing operation in this case. This means that as soon as the second pump unit has finished the suction mode, there is a completely preloaded thick matter column which can then be pressed into the delivery line by switching to the pump mode. Thus, no time losses are created by the precompressing operation.
Irregularities in the delivery flow, in particular a slumping back of the thick matter column into the delivery line can be reduced according to one variant in that a pressure is built up in the suction line by precompression, the pressure being substantially identical with the pressure in the delivery line during the pump mode. During switching from the one to the other pump unit, the precompressed thick matter comes into contact with the thick matter in the delivery line. Since both have substantially the same pressure, no vibrations are created in the thick matter column.
For a further optimization of the switching operation, a further embodiment provides for an operation in which during a switching process from the first to the second pump unit both pump units work at half the volume flow in the pump mode. Overlaps which occur during the switching operation, e.g. due to a switching valve, are thereby compensated. A delivery flow which is as constant as possible is the result also during the switching process.